Color blindness is a common disease of damaged color vision or no color vision, which is generally caused by genetic factors. The colorblind people may lack an ability to recognize some certain colors or cannot recognize any color at all. According to statistics, colorblind men accounted for about 8% of the total male population, while colorblind women accounted for about 0.5% of the total female population. The life and the work of the colorblind people may be severely affected by this disease.
There are three types of cone cells on a human retina. i.e. a L-cone cell being sensitive to the lights with long wavelengths of 535-575 nm, a M-cone cell being sensitive to the lights with medium wavelengths of 500-550 nm, and a S-cone cell being sensitive to the lights with short wavelengths of 400-450 nm. The color blindness is caused by absence or mutation of the cone cells on the retina. For example, the absence of the L-cone cell causes red two-color blindness, the absence of the M-cone cell causes green two-color blindness, and the absence of the S-cone cell causes blue two-color blindness. Both the red two-color blind people and the green two-color blind people cannot distinguish the red color from the green color, and the blue two-color blind people cannot distinguish the blue color from the green color.
Hans Brettel proposes a two-color blind simulation model, wherein all of the colors that can be observed by each of the red two-color blind people, the green two-color blind people and the blue two-color blind people are concentrated on two planes; however, an angle of such two planes is so small that the two planes is almost equal to one plane, which is called a color plane for the two-color blindness. As a result, a simplified two-color blind module is established.
As mentioned above, the two-color blindness is caused by the absence of one of the three types of cone cells, and such absence corresponds to variant of a particular signal and invariant of two other particular signals in a LMS space. Thus, the red two-color blindness, the green two-color blindness and the blue two-color blindness can be represented by projecting colors in the RGB space into respective planes in three directions of L, M and S. Researchers have found that the red two-color blind people and the green two-color blind people are incompetent in distinguish the red color from the green color, because the red color and the green color are distributed on two sides of the color plane for the red two-color blindness or the green two-color blindness respectively, and thus the red color and the green color may be overlapped with each thus and confused upon being projected onto the color plane. The blue two-color blind people are incompetent in distinguishing the blue color from the green color, because the blue color and the green color are distributed on two sides of the color plane for the blue two-color blindness.
In prior art, an image may be processed by rotating a H component of each sub-pixel; however, the image may be distorted by such processing.